1. Field of the Invention
This invention relates to air dryers and more particularly to an air dryer and a reservoir, including a separate purge volume, constructed together as a module.
2. Description of Prior Art
Air dryers have been used to dry the air in a heavy vehicle air brake system for many years. The advantages of clean and dry air in air brake systems has long been recognized, as moisture entrained in the air brake system may during cold weather operation cause the components of the air brake system to freeze, thus rendering the system inoperable. These prior art air dryers normally include a desiccant material through which the compressed air flows. When the vehicle air compressor has charged the vehicle air reservoirs to a sufficient pressure level, the compressor is unloaded so that the compressor no longer compresses air. When the compressor is unloaded, a signal is transmitted to a purge valve carried within the air dryer which causes stored compressed air to backflow through the desiccant at a controlled rate to regenerate the desiccant. The air used to regenerate the desiccant can be either from compressed air stored in an integral purge volume within the air dryer or from compressed air stored in a separate reservoir.
Most prior art compressed air systems for heavy vehicle air brake applications use three reservoirs which are separate from the air dryer. A compressor feeds compressed air to the air dryer which after flowing through the desiccant bed is fed to a remote supply reservoir. The supply reservoir is connected to feed compressed air to a primary reservoir and a secondary reservoir. The primary and secondary reservoirs feed pneumatic circuits which can control the air brake system of the vehicle. For protection from loss of air pressure the primary and secondary reservoirs each include a check valve in their pneumatic connections to the supply reservoir. A pneumatic control line extends from the supply reservoir to an air pressure governor which controls loading and unloading of the air compressor.
The present invention is for an air dryer and reservoir assembly, for providing compressed air from an air compressor for operating the brakes of a heavy motor vehicle, which includes an air dryer connected to receive compressed air from the air compressor, a secondary air reservoir separate from the air dryer, a housing containing pneumatic circuit components for controlling the flow of compressed air from the air compressor through the air dryer to the secondary reservoir having the air dryer securely attached to one section thereof and the secondary reservoir securely attached to another section thereof for securing the air dryer and the secondary reservoir together as a unitary air dryer reservoir module. The compressed air brake system with the air dryer reservoir module also includes a primary air reservoir having a pneumatic connection to the housing disposed remote from the secondary air reservoir with the housing containing pneumatic circuit components for controlling compressed air flow between the air dryer and the primary air reservoir. Pneumatic circuit protection valves are disposed within the housing for monitoring the pneumatic circuits fed by the primary and secondary reservoirs. A failure detection means is also disposed within the housing for detecting a failure of the pneumatic circuits which are fed by the primary and secondary reservoirs and in the event of a failure of these pneumatic circuits the speed of the heavy vehicle is limited.
The herein disclosed air brake system""s air charging and treatment sub-system referred to as the air dryer reservoir module provides for a simplified and cost effective air charging sub-system, using integrated components. The air dryer reservoir module is configured in a way that allows the elimination of the supply reservoir, which is used in the standard three reservoir system, while providing a means of simultaneously sensing both the primary reservoir and the secondary reservoir for air compressor and air dryer control.
The air dryer reservoir module integrates components such as pressure protection valves, the air compressor governor, pressure relief valves, pressure sensors and the like in a way that eliminates the need for the supply reservoir, the supply reservoir safety valve, several of the standard three reservoir system""s external lines and many of its fittings. The reduction of components, fittings and pneumatic lines reduces potential failure modes. With respect to a standard three reservoir system, the air dryer reservoir module integrates the following components: air dryer, primary and secondary check valves, supply and secondary drain valves, supply reservoir safety valve, the compressor governor, auxiliary system pressure protection valves, and the supply and secondary reservoirs.
A purge volume can be built into the end of the secondary reservoir to which the air dryer is attached. An internal baffle separates the secondary reservoir volume from the purge volume. Internal communication passages connect the secondary reservoir and purge volume to the air dryer. The dryer reservoir module can also be constructed to equalize the pressure between the primary reservoir and the secondary reservoir, such that if the vehicle is parked for a given period of time the pressure cannot be replenished. Thereby limiting the use of the vehicle with a severely leaking reservoir.